High-density Flows Research Articles

Statistical and density-based clustering of geographical flows for crowd movement patterns recognition

With the rapid development of sensors and communication technologies, it has become easy to collect large-scale and long-term crowd movement positioning data, which brings new opportunities for studying crowd movement patterns. This paper proposes a novel Statistical and Density-Based Clustering algorithm (SDBC) to identify implicit significant spatial aggregation patterns in geographical flow data. Unlike existing flow clustering algorithms, this method identifies the hot spots of origin-destination (OD) flows based on local spatial statistics and density-growing clustering. It also evaluates the significance of the identified geographic flow clusters, effectively reducing the identification of spurious clusters generated by chance in data. In our method, the spatial neighborhood of each flow is first obtained based on spatial proximity, temporal similarity, and directional similarity. Then, the number of flows in the spatial neighborhood of each flow is calculated and used as the density measure. Based on this, high-density flows are automatically detected using local spatial aggregation statistics, and a hierarchical density-based clustering strategy is developed to merge adjacent high-density flows to generate candidate flow clusters. Finally, we perform permutation tests to infer the statistical significance of each flow cluster and eliminate the candidate clusters generated by chance. Experiments on synthetic data and real-world taxi trajectory data were conducted to evaluate the effectiveness of the proposed method. Results show that the proposed method can accurately identify the statistically significant flow clusters of different shapes and densities and performs better than the available state-of-the-art flow clustering algorithms.

Fine-grained gravity flow sedimentation and its influence on development of shale oil sweet sections in lacustrine basins in China

The geological conditions and processes of fine-grained gravity flow sedimentation in continental lacustrine basins in China are analyzed to construct the model of fine-grained gravity flow sedimentation in lacustrine basin, reveal the development laws of fine-grained deposits and source-reservoir, and identify the sweet sections of shale oil. The results show that fine-grained gravity flow is one of the important sedimentary processes in deep lake environment, and it can transport fine-grained clasts and organic matter in shallow water to deep lake, forming sweet sections and high-quality source rocks of shale oil. Fine-grained gravity flow deposits in deep waters of lacustrine basins in China are mainly fine-grained high-density flow, fine-grained turbidity flow (including surge-like turbidity flow and fine-grained hyperpycnal flow), fine-grained viscous flow (including fine-grained debris flow and mud flow), and fine-grained transitional flow deposits. The distribution of fine-grained gravity flow deposits in the warm and humid unbalanced lacustrine basins are controlled by lake-level fluctuation, flooding events, and lakebed paleogeomorphology. During the lake-level rise, fine-grained hyperpycnal flow caused by flooding formed fine-grained channel–levee–lobe system in the flat area of the deep lake. During the lake-level fall, the sublacustrine fan system represented by unconfined channel was developed in the flexural slope breaks and sedimentary slopes of depressed lacustrine basins, and in the steep slopes of faulted lacustrine basins; the sublacustrine fan system with confined or unconfined channel was developed on the gentle slopes and in axial direction of faulted lacustrine basins, with fine-grained gravity flow deposits possibly existing in the lower fan. Within the fourth-order sequences, transgression might lead to organic-rich shale and fine-grained hyperpycnal flow deposits, while regression might cause fine-grained high-density flow, surge-like turbidity flow, fine-grained debris flow, mud flow, and fine-grained transitional flow deposits. Since the Permian, in the shale strata of lacustrine basins in China, multiple transgression-regression cycles of fourth-order sequences have formed multiple source-reservoir assemblages. Diverse fine-grained gravity flow sedimentation processes have created sweet sections of thin siltstone consisting of fine-grained high-density flow, fine-grained hyperpycnal flow and surge-like turbidity flow deposits, sweet sections with interbeds of mudstone and siltstone formed by fine-grained transitional flows, and sweet sections of shale containing silty and muddy clasts and with horizontal bedding formed by fine-grained debris flow and mud flow. The model of fine-grained gravity flow sedimentation in lacustrine basin is significant for the scientific evaluation of sweet shale oil reservoir and organic-rich source rock.

DRIFTING TIMBER FORMATION ON MUDFLOW RIVERS ON SAKHALIN ISLAND

The paper considers the regional features of the phenomena of timber drifting on mudflow rivers on Sakhalin Island. The regularities of mudflow formation in Sakhalin rivers and their mudflow regime are established and the factors causing timber drifting in the debris flow watercourses of Sakhalin Island are studied. Due to the history of Sakhalin terrain and macrorelief formation, the main mountain structures are composed of marine sediments. This promotes mudflows on rivers, the active development of exogenous processes on river slopes, and the flow of solid phase and woody vegetation into the channel and talvegs. As a result, the density of streams increases, their eroding and abrasive ability rises, which affects significantly channel deformations and involves timber drifting. High-density flows have an elevated transporting capacity, since they increase the pulling force of the flow affecting the midsection of the drifting timber root system, and also raise the timber buoyancy due to an increase in the pushing Archimedean force. Also, regional features include a large amount of liquid precipitation, the annual amounts of which in the valleys and on the coast are 800–1200 mm, and in mountainous areas can reach 1500–2000 mm. The main species of drifting timber drifting include broad-leaved trees (willow and alder), which, unlike coniferous wood, are more prone to form logjams and are most hazardous for culverts.

Research on Multi -mode Power Generation Devices based on Wave Energy

This paper mainly studies a multi-mode power generation device based on wave energy, which is mainly composed of power generation device, energy storage device, monitoring device, through the use of electromagnetic machinery, piezoelectric ceramics, hydraulic system in a variety of ways to generate electricity, and then the energy storage device stable output, is a kind of power generation system will be converted into electrical energy device, to achieve high efficiency conversion of wave energy. Each part of the project is innovative and practical, which has high application value in ocean power generation. Compared with some traditional power generation devices, this device uses a new type of energy, ocean wave energy, which is a pollution-free, clean and renewable new energy. Wave energy has high flow density, huge reserves and wide distribution, which is the main direction of the development of ocean energy utilization in the future. It will make positive contributions to Marine construction, economic development and infrastructure construction of countries and regions along the Belt and Road.

Sulfur hexafluoride pulsed jet visualization by the Resonant Schlieren method

Resonant Schlieren technique combines the variation of the refractive index of the medium with the absorption of seeded particles, thus producing high contrast images. It presents low cost and a relatively easy implementation and operation, and allows visualization of low and high-density flows. This paper describes the application of the Resonant Schlieren method to visualize a pulsed free jet of sulfur hexafluoride. A piezoelectric valve with a duty cycle of 10 Hz and pulse width of 2 ms was used to control the flow through a nozzle with 1 mm diameter. Pressures in a vacuum chamber with optical windows were varied from 20 mbar to 1 bar and the flow was seeded with iodine molecules in order to increase the gas refractive index. The Schlieren images of the expanded flows presented a high contrast and the measured pulsed jet front velocities varied from 3 to 166 m/s, from subsonic to supersonic flow regimes. Numerical simulations were performed using the lattice Boltzmann method and the theoretical results showed a good agreement with experimental data.

Timing and causes of forest fire at the K–Pg boundary

We report K–Pg-age deposits in Baja California, Mexico, consisting of terrestrial and shallow-marine materials re-sedimented onto the continental slope, including corals, gastropods, bivalves, shocked quartz grains, an andesitic tuff with a SHRIMP U–Pb age (66.12 ± 0.65 Ma) indistinguishable from that of the K–Pg boundary, and charred tree trunks. The overlying mudstones show an iridium anomaly and fungal and fern spores spikes. We interpret these heterogeneous deposits as a direct result of the Chicxulub impact and a mega-tsunami in response to seismically-induced landsliding. The tsunami backwash carried the megaflora offshore in high-density flows, remobilizing shallow-marine fauna and sediment en route. Charring of the trees at temperatures up to > 1000 °C took place in the interval between impact and arrival of the tsunami, which on the basis of seismic velocities and historic analogues amounted to only tens of minutes at most. This constrains the timing and causes of fires and the minimum distance from the impact site over which fires may be ignited.

Density-based clustering for bivariate-flow data

Geographical flows reflect the movements, spatial interactions or connections among locations and are generally abstracted as origin-destination (OD) flows. In this context, clustering is a spatial pattern describing a group of flows with adjacent O and D points. For data composed of two types of flows (bivariate-flow data), a bivariate-flow cluster is a cluster comprising two types of flows, at least one of which exhibits a clustering pattern. In a bivariate-flow cluster, varying flow density combinations imply different meanings. For instance, a cluster with high-density travel flows on both weekdays (type A) and weekends (type B) may be associated with entertainment, whereas high-density flows on weekdays and sparse flows on weekends may reveal work-related travel. However, identifying bivariate-flow clusters with different flow density combinations is still an unsolved problem. To this end, we extend a bivariate-point clustering method and propose a density-based clustering method for bivariate flows. The simulation experiments verify model robustness. In a case study, we apply this method to extract clusters of bivariate-flow data comprising Beijing taxi OD flows of different periods, and identify clusters of work-related, entertainment, tourism, or egress and return travels. These results demonstrate the capability of our method in detecting bivariate-flow clusters.

Exploring the predictive power of seismic geomorphology to assess sedimentary characteristics of gravity-flow deposits: examples from offshore East and West Africa reservoirs

Abstract This research seeks to test the hypothesis that the rheology of submarine gravity-flows influences the planform geometry of associated fan lobe deposits. If this control exists, seismic geomorphology has the potential to predict the sedimentary characteristics of these deposits by analysing relatively simple seismic outputs such as time structure maps and amplitude maps. This predictive power could potentially aid the identification of prospective reservoirs through automated processes of seismic interpretation. In this work, Upper Cretaceous and Neogene deep-water reservoirs from East and West Africa with porosity in excess of 20% and multi-Darcy permeability were analysed. The overall external geometry of the reservoirs was described by integrating seismic amplitude extractions, structure and isochron maps derived from high-quality 3D seismic data. The maps were generated from detailed interpretation of the top and base reservoir reflections. Core photos of the reservoirs were integrated into the seismic project and their examination allowed the identification of dominant sedimentary facies, enabling a proposal for the classification of these deposits in terms of flow processes. The research indicates that the confinement of flows exerts an obvious control on the shape of the deposits and results in sedimentary bodies with marked elongation at the seismic scale. However, analysis of the reservoirs at the core scale indicated that they are dominated by massive, poorly sorted, medium- to coarse-grained sandstones, commonly with floating oversize clasts, as well as beds with disrupted laminae and sandy conglomerates. These characteristics may indicate ‘depositional freezing’ from high-density flows with yield strength, which may also have contributed to the limited lateral spread of the deposits analysed. The research also highlights the importance of the non-unique relationship between sedimentary processes and external geometries of the resulting deposits at the seismic scale. This means that deposits with similar geometries may have markedly different sedimentary characteristics. This work highlights the increasing importance of integrating detailed seismic geomorphology studies with an accurate examination of core data to validate models of gravity flow processes and test their predictive value.

Correlation of retinal alterations with vascular structure of macular neovascularisation in swept-source optical coherence tomography angiography in age-related macular degeneration

PurposeThe aim of this study was to find out whether the vascular architecture of untreated macular neovascularisations (MNV) in neovascular age-related macular degeneration (nAMD) as visualised with optic coherence tomography angiography (OCTA) is associated with functional and known morphological alterations of the retina in optic coherence tomography (SD-OCT).MethodsThe study design was retrospective with consecutive patient inclusion. In 107 patients with newly diagnosed nAMD, MNV were detected by means of OCTA and automated quantitative vascular analysis was performed. The MNV characteristics measured were area, flow density, total vascular length (sumL), density of vascular nodes (numN), fractal dimension (FD) and average vascular width (avgW). These parameters were assessed for associations with vision (BCVA), central retinal thickness (CRT), fluid distribution, the elevation of any pigment epithelial detachment (PED), the occurrence of subretinal haemorrhage and atrophy.ResultsBCVA was significantly worse with greater MNV area and sumL. Fluid distribution differed significantly in relation to area (p < 0.005), sumL (p < 0.005) and FD (p = 0.001). Greater PED height was significantly associated with higher numN (p < 0.05) and lower avgW (p < 0.05). Atrophy was present significantly more often in MNV with larger area (p < 0.05), higher sumL (p < 0.05) and higher flow density (p = 0.002). None of the MNV parameters had a significant association with CRT or the occurrence of haemorrhage.ConclusionOCTA is not restricted to evaluation of secondary changes but offers the opportunity to analyse the vascular structure of MNV in detail. Differences in vascular morphology are associated with certain secondary changes in retinal morphology. There are thus grounds for optimism that further research may identify and classify OCTA-based markers to permit more individualised treatment of nAMD.

Analyzing the delays of target lane vehicles caused by vehicle lane-changing operation

Vehicle lane-changing on urban roads is the most common traffic behavior, in which the driver changes the direction or increases the speed of the vehicle by changing its trajectory. However, in high-density traffic flow, when a vehicle changes lanes, a series of vehicles following the target vehicle in the target lane will be delayed. In this study, DJI Phantom 4 drones were used to vertically record the traffic on a road section. Tracker software was then used to extract vehicle information from the video taken by the drones, including the vehicle operating speeds, etc. SPSS 22 and Origin analysis software were then employed to analyze the correlations between different vehicle operating parameters. It was found that the operating speed of the first vehicle following the target vehicle in the target lane is related to the speeds and positions of both the target vehicle and the vehicle preceding it. Under the condition of high-density traffic flow, when the target vehicle is inserted into the target lane, the speed of the vehicles following the target vehicle in the target lane will change. To model this process, the corresponding Sine and DoseResp models were constructed. By calculating the delays of vehicles following the target vehicle in the target lane, it was concluded that the overall delay of the fleet is 3.9–9.5 s.

A Combined Volume of Fluid and Immersed Boundary Method for Modeling of Two-Phase Flows With High Density Ratio

Abstract A combined volume of fluid and immersed boundary method is developed to simulate two-phase flows with high density ratio. The problems of discontinuity of density and momentum flux are known to be challenging in simulations. In order to overcome the numerical instabilities, an extra velocity field is designed to extend velocity of the heavier phase into the lighter phase and to enforce a new boundary condition near the interface, which is similar to nonslip boundary conditions in fluid–structure interaction problems. The interface is captured using a volume of fluid method, and a new boundary layer is built on the lighter phase side by an immersed boundary method. The designed boundary layer helps to reduce the spurious velocity caused by the imbalance of dynamic pressure gradient and density gradient and to prevent tearing of the interface due to the tangential velocity across the interface. The influence of time-step, density ratio, and spatial resolution is studied in detail for two set of cases, steady stratified flow and convection of a high-density droplet, where direct comparison is possible to potential flow analysis (i.e., infinite Reynold s number). An initial study for a droplet splashing on a thin liquid film demonstrates applicability of the new solver to real-life applications. However, detailed comparisons should be performed in the future for finite Reynold s number cases to fully demonstrate the improvements in accuracy and stability of high-density ratio two-phase flow simulations offered by the new method.

Application of mineral liberation analysis (MLA) for investigations of grain size distribution in submarine density flow deposits

Textural and structural features of submarine mass density flow sediments are a record of depositional flow evolution and hydrodynamics. Record of changes in such flow movement are difficult or impossible to detect, especially in fine sediments, without quantitative grain size analysis. This study shows an automated measurement system of mineral liberation analysis MLA applied for the first time to grain size distribution. The analysis concerns heavy minerals extracted from very fine- and fine-grained sandstones of the Cergowa Beds (Lower Oligocene) in the Polish and Slovak Outer Carpathians, which macroscopically show unclear textural trends and represent deposits of steady and uniform turbidity currents, possibly initiated by hyperpycnal effluents. The MLA analysis showed that the tested material represents sediments deposited by flows with developing turbulence. Simultaneously, the study verified that a turbulence damping contributes to size-density sorting during transport and demonstrated that maximum rather than average grain size is controlled by flow concentration, therefore reflects flow hydrodynamics. Besides, MLA measurements recognised variations in flow motion recorded by three types of grain-size breaks: (i) in high-density flow when capacity-controlled conditions are changing so that high energy flow erodes the previously deposited material; (ii) at a sharp interface between high-concentration basal layer and the overriding flow with lower concentration, and (iii) at a transition between low- and high-density flows during deposition of the Bouma interval Tb or between Tb and Tc. The MLA test study appears to be promising because this method increases objectivity of large amount of data collection, therefore provides significant statistical representation. Besides, this automated system reduces human errors, bias and tedious manual analyses, thus opening new perspectives in analysis of detrital sediments and interpretation of depositional processes.

Investigating safety impact of sun glare in urban tunnels based on cellular automata approach

This study applies a simulation-based traffic conflict technique to evaluate the hypothesis that sun glare under upper vents exerts negative impacts on traffic safety in urban tunnels. A modified cellular automata (CA) model is applied to simulate the deceleration behavior due to sun glare (DBSG) in real traffic. And the model is calibrated and validated against the empirical data. Conflict occurrences are generated through simulating vehicular interactions based on this model. Simulation experiments are conducted with different density and illuminance to evaluate the safety impacts of sun glare. Comparison of simulated conflict occurrences shows that rear-end conflicts occur more frequently as illuminance and density get higher. And the impacts of sun glare are more obvious on weak conflicts in moderate-density flow and more severe conflicts in high-density flows, respectively. To alleviate the negative impacts of sun glare, a sunshade system is designed based on the quantitative results.

Modeling uranium and 226Ra mobility during and after an acidic in situ recovery test (Dulaan Uul, Mongolia)

This article presents the results of groundwater monitoring over a period of six years and the interpretation of these results by a reactive transport model, following an In Situ Recovery (ISR) test on the Dulaan Uul uranium deposit in Mongolia. An environmental monitoring survey was set up using 17 piezometers, from which it has been possible to describe the changes in the water composition before, during and after the ISR test. The water quality before the start of mining activities rendered it unfit for human consumption. During and after the test, a descent of the saline plume was observed, resulting in a dilution of the injection solutions. After a rapid decrease to pH = 1.13 during the production phase of the ISR test, the pH stabilized at around 4 in the production area and 5.5 below the production cell one year after the end of the test. Uranium and radium were being naturally attenuated. Uranium returned to background concentrations (0.3 mg/L) after two years and the measured 226Ra concentrations represent no more than 10% of the expected concentrations during production (75 Bq/L). The modeling of the contaminants of concern mobility, namely pH and concentrations of sulfate, uranium and 226Ra, is based on several key complementary mechanisms: density flow, cation exchange with clay minerals and co-precipitation of 226Ra in the barite. The modeling results show that the observed plume descent and sulfate dilution can only be predicted if consideration of a high-density flow is included. Similarly, the changes in pH and 226Ra concentration are only correctly predicted when the cationic exchanges with the clays and the co-precipitation reaction within the barite using the solid solution theory are integrated into the models. Finally, the proper representation of the changes in water composition at the scale of the test requires the use of a sufficiently fine mesh (1 m × 1 m cell) to take into account the spatial variability of hydrogeological (permeability distribution in particular) and geological (reduced, oxidized and mineralized facies distributions) parameters.

Magnetochronology applied to assess tempo of turbidite deposition: A case study of ponded sheet-like turbidites from the lower Miocene of the northern Apennines (Italy)

This paper investigates the magnetostratigraphy of the ~750 m-thick Costa Grande Member (lower Miocene) from the Castagnola Basin of NW Italy, which represents the turbidite fill of a structurally confined basin where flow ponding resulted in a complete record of deposition from diverse sediment gravity flow types. The magnetostratigraphic profile of the Costa Grande Mb was correlated to the Geomagnetic Polarity Timescale using a well-established statistical method devised to be applied to sedimentary successions with steady accumulation rate. The results of the correlation exercise, validated with the available biostratigraphy, indicate an early Miocene age (from Chron C6AAr.3r to C6Bn.2n) between 21.7 and 22.3 Ma. The obtained age model was then used to calculate accumulation rates and frequencies of small volume and low-density vs. large volume and high-density gravity flows over an estimated 650 kyr time span. Results show that low-density flows contributed at a constant pace of 545 m Myr−1 to sediment accumulation, depositing relatively thin-bedded turbidites with a minimum recurrence time of 1.7 kyr, whereas the high-density flows, which are at least four times less frequent, are clustered in the stratigraphy, and become more abundant up-section. We also show that the minimum sediment volumes discharged by high-density flows suggest triggering by submarine failures whose recurrence and magnitude were probably not random. Lastly, we propose that the statistical method used in this study to correlate the Costa Grande Mb magnetostratigraphy to the GPTS provides best results when the products of episodic but voluminous depositional events are carefully identified and removed.

Sedimentary facies related to supercritical-flow bedforms in foreset slopes of a Gilbert-type delta (middle Pleistocene, central Japan)

Bedforms related to supercritical flows and hydraulic jumps have been increasingly recognized in various depositional environments. However, few ancient examples have been investigated in terms of the variations and transitions of supercritical-flow deposits. We present a detailed analysis of the sedimentary facies and stacking patterns of cyclic step, chute-and-pool, and antidune deposits of a coarse-grained Gilbert-type delta in the middle Pleistocene Kamiizumi Formation, Shimosa Group, central Japan. The Kamiizumi Formation was deposited during marine isotope stages 8–7.5 in the paleo-Tokyo Bay basin. We describe the following four facies and two facies successions in the foreset beds exposed at the study site. Planar-parallel stratification represents antidune to subcritical deposits from high-density flows. Deep scours infilled by steeply dipping backsets are interpreted as chute-and-pool deposits. Shallow, lenticular troughs infilled with backsets and foresets are interpreted as chute-and-pool and unstable antidune deposits. Lenticular units of fine sand with low-angle backsets of considerably greater wavelength than the other three facies are indicative of cyclic step deposits. One facies succession is characterized by chute-and-pool deposits alternating antidune to subcritical deposits formed during progradation of foresets. The lateral cyclicity of coarser-grained chute-and-pool deposits and finer grained antidune to subcritical deposits is characteristic of autogenic flow changes on progradational steep delta slopes. The other facies succession represents an aggradational delta succession from cyclic step deposits, to chute-and-pool deposits, to antidune to subcritical deposits. The vertical changes indicate decreasing flow velocity and may be the result of autogenic flow transitions during rapid aggradation. These facies changes resulted from the intrinsic instability of supercritical flows on steep foreset slopes at high depositional rates.

PENENTUAN PRIORITAS PENANGANAN BANJIR GENANGAN BERDASARKAN TINGKAT KERAWANAN MENGGUNAKAN TOPOGRAPHIC WETNESS INDEX Studi Kasus di DAS Solo

The increasing frequency of flood events is an indication of the failure of watershed management. Natural resource utilization activities in the Solo watershed tend to be intensive from upstream to downstream, cause a decrease in the carrying capacity of the watershed. To restore the carrying capacity of the watershed, efforts are needed to monitor and evaluate watersheds. The initial stage that needs to be done is to ensure the accuracy of the flood-prone areas by determining priority areas. The purpose of the study is to determine the flood-prone areas in the Solo watershed based on the level of flood vulnerability. Flood vulnerability is influenced by topographic conditions. The Topographic Wetness Index (TWI) method was used to determine the flood-prone areas. The high TWI value indicates that the area has high flood vulnerability and is associated with flat topography with high flow density. This method is based on raster data was derived from DEM 30 m data which is reduced to slope through spatial analysis tools and the accumulation flow is analyzed using Watershed Delineation Tools (WDT). Based on the results of the analysis, the priority of flood handling is determined in the criterion-very vulnerable area with TWI 11.65-38.30 identified as 387098.23 ha (39.68%). Flood handling in the Solo watershed is prioritized on 1) Bojonegoro Regency covering 105215.13 ha, 2) Ngawi (56810.68 ha), 3) Madiun (44102.06 ha), 4) Tuban covering an area of 43072.06 ha, and 5) Ponorogo (35853.62 ha).

Studying Non-coaxiality in Non-lane-based Car-following Behavior

In this paper, in order to study non-lane-based car-following, the non-coaxiality concept is defined, where there is a significant lateral difference between the leader and follower vehicle. Two main reasons for non-coaxiality were addressed by drivers in the interview: providing more visible distances beyond leader vehicle and increasing the possibility of escaping in sudden brakes to avoid rear-end collision. Results showed that non-lane-based behavior was due to the effect of the existence of other cars in the traffic flow. By reducing speed or increasing density, vehicles more affect each other. But this trend will continue up until vehicles fill the free spaces. In other words, vehicles make others stick to the leader’s path in high-density flow. Studying the relationship between lateral distance and time headway demonstrated that time headway threshold for initiation of car-following behavior in Iranian drivers can be approximately 2 seconds. In this study, Overtaking was defined as a part or continuation of the non-lane-based driving behavior. For overtaking on the left, steering angle, the final lateral distance and the lateral speed difference between the follower and leader were 33%, 28% and 15% less than overtaking on the right.

Different initial density turbidite sediments with coarse grain injection and their corresponding flow pattern: Additional insights from numerical simulation in a study case of South China Sea

The work presents the sedimentology and depositional results of the turbidity flow from Miocene to Pliocene along the North Slope of South China Sea (SCS). The integration of the core-log-seismic data has enabled us to clarify turbidity flow with different density and characterize their corresponding seismic geomorphic sedimentation. Based on the differences between the initial density and the later, we classified the turbidity flow into two types, namely: low- and high-density flow with coarse grain injection. According to the hydrodynamic numerical simulation results, we constructed different subcritical turbidity flow models with various density and rebuilt the depositional pattern along the slope. As to the numerical simulation model, we introduced the erosion rate into the classical full Reynolds-averaged N-S (RANS) equation, which is suitable to the deep-sea slope area. Through comparison of the above simulation models, the results show that the high-density turbidites with coarse-grained injection are mostly developed with lower vertical erosion rates and higher lateral abrasion rates. They are characterized with multi-branched and lobe-shaped sedimentary volumes, while low-density turbidites with coarse-grained injection are characterized with higher vertical erosion rates and lower lateral abrasion rates. And this kind of turbidites can generate single-branched and banding deposits. In addition, the fluctuating sea levels and the varying topographies are important to influence the subcritical turbidity flow models in the deep-water slope.

A multidisciplinary study of ecosystem evolution through early Pleistocene climate change from the marine Arda River section, Italy

AbstractThe Arda River marine succession (Italy) is an excellent site to apply an integrated approach to paleoenvironmental reconstructions, combining the results of sedimentology, body fossil paleontology, and ichnology to unravel the sedimentary evolution of a complex marine setting in the frame of early Pleistocene climate change and tectonic activity. The succession represents a subaqueous extension of a fluvial system, originated during phases of advance of fan deltas affected by high-density flows triggered by river floods, and overlain by continental conglomerates, indicating a relative sea level fall and the establishment of a continental environment. An overall regressive trend is observed through the section, from prodelta to delta front and intertidal settings. The hydrodynamic energy and the sedimentation rate are not constant through the section, but they are influenced by hyperpycnal flows, whose sediments were mainly supplied by an increase in Apennine uplift and erosion, especially after 1.80 Ma. The Arda section documents the same evolutionary history of coeval successions in the Paleo-Adriatic region, as well as the climatic changes of the early Pleistocene. The different approaches used complement quite well one another, giving strength and robustness to the obtained results.